The present invention relates to a calculator which displays an input equation by means of characters.
A calculator can be used to perform calculations by inputting numerical information and function information according to a calculating formula for obtaining calculation results with ten numerical keys and function keys of +, -, .times., .div., and so on of the keyboard. Since the display condition does not change when the function keys are operated, it is difficult to see which function key has been operated, or whether in fact it has been operated at all. A calculator has been thus proposed in which characters such as "+", "-", ".times.", ".div." and so on are displayed when the corresponding function keys are operated for confirming the input condition.
However, with such a calculator, it is only possible to confirm which key has been most recently operated, and it is not possible to confirm whether calculations are being performed according to the desired formula as a whole.
For performing operations of a long formula, especially with a calculator of the operation type according to the perfect algebraic method, the series of key operations is long. This leads to frequent key operation errors, and the operator becomes unsure whether or not the key input has been correctly performed according to the formula.
Even when the operator becomes aware of a key operation error, it is only possible to correct the key operation which has just been operated. Since it is impossible to correct other data whose input has been completed, the key operations must be performed once again from the beginning.
It is, therefore, the primary object of the present invention to provide a calculator in which the input condition of the information according to the calcuation formula for obtaining the calculation result is displayed by a character formula universally representing the kinds and sequences of the operations according to the calculation formula, so that confirmation of the input condition may be performed with ease and key operation errors may be prevented.
It is another object of the present invention to provide a calculator according to which it is possible to confirm the actual input data corresponding to any character of the character formula.
It is still another object of the present invention to provide a calculator according to which it is possible to change the data corresponding to any character of the character formula.
It is still another object of the present invention to provide a calculator according to which the display of the character formula may be held after the operations of the calculation formula for obtaining the calculation result have been completed, so that the operations may be repeated by substituting new data corresponding to any character in the character formula.